Process for extreme pressure lubricants



Patented May 9, 1939 UNITED STATES PATENT OFFICE- PROCESS FOR EXTREME PRESSURE LUBRICANTS No Drawing. Application November 14, 1936, Se-

rial No. 110,930. 2, 1935 2 Claims.

This invention relatesto lubricants suitable for lubrication under extreme pressure conditions.

It is well known that the high pressures occurring in certain types of gears and bearings may 5 cause a film of lubricant to rupture with consequent damage to the machinery. It has been shown that mineral oil lubricants can be improved with regard to their load-carrying capacity by the addition of certain substances to a degree which enables them to protect successfully rubbing metal surfaces under extreme pressures. Excessive wear, sending and seizure which normally follow a break in the film of lubricant can thus be prevented even under the most unfavorable pressure and speed conditions. Oils possessing this highly desirable property are called extreme pressure lubricants.

Among the substances that have been proposed for incorporation into lubricating oils for the purpose of improving their extreme pressure properties, esters of phosphorus acids have been suggested. The terms phosphorus acids or phosphorus esters as herein used refer to the acids and esters respectively of the three and five valent phosphorus, such as phosphorous and phosphoric acids, or esters thereof. It is known 'that suitable phosphorus esters may contain organic radicals selected from the class of alkyl, aralkyl, a'ryl and heterocyclic radicals, which in turn may contain substitution groups such as 0H, -SH, :8, ---COOH, --NH2, =00, =0, etc. Below are a few examples of phosphorus alkyl and aryl esters which have proven to be particularly useful as extreme pressure dopes:

tri-alkyl phosphites or phosphates, in which the alkyl groups contain from 8 to 20 carbon atoms, tri-phenyl and tri-cresyl phosphates, reaction products of phosphoric acid and castor oil, etc.

Besides phosphorus-bearing substances many otherelements and compounds are known to possess extreme pressure properties. Among them are: sulfur, chlorine, and their organic derivatives, organic suite-chlorides, and members of metal-organic compounds, such as disclosed in the Van Peski-Van Melsen application Serial No.

81,712 filed May 25, 1936.

We have discovered that the extreme pressure properties of extreme pressure compounds, particularly those of phosphorus esters, can be considerably enhanced by adding to the mineral oil containing same a relatively small amount of a higher polycarboxylic acid, i. e. a polycarboxylic acid which has at least 10 carbon atoms.

Suitable carboxylic acids are, for instance,

alkenyl succinic acid of 10 and "more carbon In the Netherlands December drolyzing the latter to liberate the free acid.

Polymerized fatty acids may be used, such as are obtained by polymerizing fatty acids with a catalyst of the type of boron fluoride, aluminum chloride, etc. or with silent electric discharges; or by polymerizing a fat and liberating polymerized fatty acids from the polymerized fat by hydrolysis or saponiflcationand acidification; or by chlorinating a fatty acid and subjecting the chlorinated product to the action of an alkali metal oran alkali alcoholate under conditions to effect complete removal of the chlorine and condensation of the fatty acid. Natural polycarboxylic acids of the requisite number of carbon atoms, such as agaric acid, are suitable as well.

The'quantities of polycarboxylic acid necessary to effect a substantial improvement in the extreme pressure properties oi! extreme pressure compounds vary from. about .1 to 10% of the weight of the oil. Excellent results are usually obtained with quantities less than 5% of the order of about 13%, the necessary quantities varying somewhat with the type and amount of extreme pressure compounds contained in thelubricating oil. If it is desired to produce an oil of a certain minimum load-carrying capacity, the addition of polycarboxylic acids as herein described will result in a considerable saving of extreme pressure compounds. 1

When oils containing certain extreme pressure compounds such as phosphorus esters or sulfochlorides are used under conditions during which water can accumulate and mix therewith, there is great danger of hydrolyzing such esters or chlorides and liberating mineral acids, which acids are highly corrosive. Since the high molecular weight polycarboxylic acids are powerful corrosion inhibitors, this danger of possible corrosion by free mineral acid is practically eliminated, or at least greatly reduced.

In the examples below the beneficialefiect of polycarboxylic acids on the extreme pressure properties of an oil containing extreme pressure compounds is shown:

Example 1.A mineral lubricating oil containing 10% of a metal organic double compound of the type described in the Van Peski-Van Melsen application Serial No. 31,712, filed May 25, 1936, consisting of cupro-bromide and di-normal butyl sulfide, showed in the Timken extreme pressure apparatus an O K value of 25. Upon addition of 2 oi voltolized oleic acid and of cetenyl succinic acid the O K value rose to 50.

Example 2.-The addition of 1% of a voltolized oleic acid to an extreme pressure lubricant consisting of a mineral oil containing 2% paratoluene sulfochloride caused the O K value on the Timken apparatus to rise from 45 to 52, aside from completely inhibiting a slight corrosive action 01 the lubricant.

Example 3.A mineral lubricating oil containing 2% oi tri-cresyl phosphate, when subjected to the Floyd's test, gave rupture of the film at 200 F. and a pressure of 325 lbs. after minute. Upon addition of /270 by weight oi voltolized oleic acid the lubricant stood the complete Floyd's test; when raising the pressure after the test, rupture only occurred at a pressure exceeding 475 lbs.

We claim as our invention:

1. An extreme pressure lubricant comprising a predominant quantity of a mineral lubricating oil, an organic compound having extreme pressure properties containing at least one of the elements oi the group consisting of phosphorus, sulfur and chlorine, and a small quantity of an alkenyl succinic acid having at least 10 carbon atoms. v

2. An extreme pressure lubricant comprising a mineral lubricating oil containing from .1 to 10% by weight of an organic compound having extreme pressure properties which contains at least one of the elements of the group consisting of phosphorus, sulfur and chlorine, and less than 5% oi' an alkenyl succinic acid having at least 10 carbon atoms.

ADRIANUB JOHANNES VAN PESH. FRANZ RUDOLF MOSER. 

